Terminal apparatus, base station apparatus, and communication method

ABSTRACT

Provided is a cyclic shift sequence generation method which can prevent coming of an interference wave into a desired wave detection window even if a cyclic shift sequence has a high mutual correlation in different bandwidths, thereby improving a channel estimation accuracy in a base station. In this method, a cyclic shift sequence number to be allocated to a cell is decided in advance. Moreover, when the cyclic shift amount between cyclic shift sequences allocated in cells is Δ 1  and the cyclic shift amount of the cyclic shift sequences allocated between the cells is Δ 2, Δ1  and Δ 2  are made different when generating a cyclic shift sequence.

This is a continuation application of application Ser. No. 12/665,012filed Dec. 16, 2009, which is a national stage of PCT/JP2008/001559filed Jun. 17, 2008, which is based on Japanese Application No.2007-160347 filed Jun. 18, 2007, the entire contents of each of whichare incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to a cyclic shift sequence generatingmethod, radio communication terminal apparatus and radio communicationbase station apparatus for generating cyclic shift sequences from aCAZAC (Constant Amplitude and Zero Auto-correlation Code) sequence suchas a Zadoff-Chu sequence used as a reference signal.

BACKGROUND ART

In a radio communication system represented by the 3GPP LTE (3rdGeneration Partnership Project Long-Term Evolution) system, studies areunderway to adopt a Zadoff-Chu sequence (hereinafter “ZC sequence”)having low inter-sequence correlation, low Peak to Average Power Ratio(PAPR) characteristic and flat frequency response characteristic, as areference signal for channel estimation. This ZC sequence is a kind of aCAZAC sequence, and represented by following equation 1 in the timedomain.

$\begin{matrix}{\mspace{79mu} \left( {{Equation}\mspace{14mu} 1} \right)} & \; \\{{f_{r}(n)} = \left\{ \begin{matrix}{{\exp \left\{ {\frac{{- {j2\pi}}\; r}{N}\left( {\frac{n\left( {n + 1} \right)}{2} + {pk}} \right)} \right\}},} & {{{when}\mspace{14mu} N\mspace{14mu} {is}\mspace{14mu} {odd}},{n = 0},1,\ldots \mspace{14mu},{N - 1}} \\{{\exp \left\{ {\frac{{- {j2\pi}}\; r}{N}\left( {\frac{n^{2}}{2} + {pk}} \right)} \right\}},} & {{{when}\mspace{14mu} N\mspace{14mu} {is}\mspace{14mu} {even}},{n = 0},1,\ldots \mspace{14mu},{N - 1}}\end{matrix} \right.} & \lbrack 1\rbrack\end{matrix}$

Here, N is the sequence length, r is the ZC sequence number in the timedomain, and N and r are coprime. Also, p is an arbitrary integer(generally p=0). Although a case will be explained below where thesequence length N is an odd number, a case is also possible where thesequence length N is an even number.

A cyclic shift ZC sequence or ZC-ZCZ (Zadoff-Chu Zero Correlation Zone)sequence, acquired by cyclically shifting the ZC sequence represented byequation 1 in the time domain, is represented by following equation 2.

$\begin{matrix}\left( {{Equation}\mspace{14mu} 2} \right) & \; \\{{{f_{r,m}(n)} = {\exp \left\{ {{\frac{{- {j2\pi}}\; r}{N}\left( \frac{\left( {n \pm {m\; \Delta}} \right)\left( {{n \pm {m\; \Delta}} + 1} \right)}{2} \right)} + {pn}} \right\}}},{{when}N{isodd}},{n = 0},1,\ldots \mspace{14mu},{N - 1}} & \lbrack 2\rbrack\end{matrix}$

Here, m is the cyclic shift sequence number, and Δ is the cyclic shiftinterval. The “±” sign may be either plus or minus. Further, thesequence transformed into a frequency domain sequence by performing aFourier transform of the time domain ZC sequence of equation 1, is alsoa ZC sequence, and, consequently, the frequency domain ZC sequence isrepresented by following equation 3.

$\begin{matrix}\left( {{Equation}\mspace{14mu} 3} \right) & \; \\{{{F_{u}(k)} = {\exp \left\{ {\frac{{- {j2\pi}}\; u}{N}\left( {\frac{k\left( {k + 1} \right)}{2} + {qk}} \right)} \right\}}},{{when}\mspace{14mu} N\mspace{14mu} {is}\mspace{14mu} {odd}},{k = 0},1,\ldots \mspace{14mu},{N - 1}} & \lbrack 3\rbrack\end{matrix}$

Here, N is the sequence length, u is the ZC sequence number in thefrequency domain, and N and u are coprime. Also, q is an arbitraryinteger (generally q=0). Similarly, given that a cyclic shift and phaserotation form a Fourier transform pair, a frequency domainrepresentation of the time domain ZC-ZCZ sequence of equation 2 isrepresented by following equation 4.

$\begin{matrix}\left( {{Equation}\mspace{14mu} 4} \right) & \; \\{{{F_{u,m}(k)} = {\exp \left\{ {{\frac{{- {j2\pi}}\; u}{N}\left( {\frac{k\left( {k + 1} \right)}{2} + {qk}} \right)} \pm {\frac{{j2\pi\Delta}\; m}{N}k}} \right\}}},{{{when}N{is}}\; {odd}},{k = 0},1,\ldots \mspace{14mu},{N - 1}} & \lbrack 4\rbrack\end{matrix}$

Here, N is the sequence length, u is the ZC sequence number in thefrequency domain, and N and u are coprime. Also, in is the cyclic shiftsequence number, Δ is the cyclic shift interval, and q is an arbitraryinteger (generally, q=0).

With the ZC sequence represented by equation 4, two kinds of sequencesof different sequence numbers (u) and sequences of different cyclicshift sequence numbers (m) can be used as reference signals (see FIG.1). These sequences of different sequence numbers (u) semi-orthogonal toeach other (i.e. these sequences have low correlation and aresubstantially orthogonal to each other), and the sequences of differentcyclic shift sequence numbers (m) are orthogonal to each other in theperiod for a cyclic shift interval (Δ), providing good cross-correlationcharacteristics between sequences. Here, given the characteristics ofCAZAC sequences, sequences of different cyclic shift values (mΔ) make iteasy to provide orthogonality between cells between which framesynchronization is established.

Non-Patent Document 1 and Non-Patent Document 2 are directed toincreasing reuse factors of sequences, and, as shown in FIG. 2, proposeallocating different cyclic shift sequence numbers (m) of the samesequence number (u) between cells (e.g. cells that belong to the samebase station) between which frame synchronization is established (Method1). For example, cells between which inter-frame synchronization isestablished use ZC sequences of the same sequence number (u), cell #1uses cyclic shift sequence numbers m=0 and 1, and cell #2 uses cyclicshift sequence numbers m=2 and 3. That is, if the cyclic shift intervalΔ is 3, cell #1 uses sequences acquired by cyclically shifting a ZCsequence (m=0) through 0 and 3 samples, and cell #2 uses ZC sequencesacquired by cyclically shifting the ZC sequence (m=0) through 6 and 9samples.

The receiving side has detection ranges (i.e. detection windows) tomatch allocated cyclic shift sequence numbers, and, as shown in FIG. 3,can separate the reference signal of the subject cell from receivedsignals by removing signals outside detection windows. For example, cell#1 separates a signal of that cell from the received signals by usingonly the detection windows of cyclic shift sequence numbers m=0 and 1.Further, as a precondition to perform this separation, each terminalneeds to transmit a reference signal at the same time using the sametransmission frequency band, and different cyclic shift sequence numbers(m) need to be set between reference signals.

Also, as shown in FIG. 4, in each cell, the cyclic shift sequence numberm is allocated which is common between the numbers of RB's (ResourceBlocks) (i.e. between frequency bandwidths). For example, regardless ofthe number of RB's, cyclic shift sequence numbers m=0 and 1 areallocated to cell #1, and cyclic shift sequence numbers m=2 and 3 areallocated to cell #2.

Although ZC sequences of different sequence numbers (u) aresemi-orthogonal to each other as described above, it is known that thereare combinations of sequence numbers between which the maximum value ofcross-correlation is large, among ZC sequences of different sequencelengths (N). For example, sequences having close ratios of the ratio ofsequence number (u) to sequence length (N) (i.e. u/N), have a highcross-correlation value. If ZC sequences having such a relationship areutilized in neighboring cells, there is a possibility that a largecross-correlation value (i.e. interference peak) appears in thedetection range of the subject cell. With correlation results includingthe desired waves and interference waves included in the detectionrange, a base station cannot identify to which cell a terminal havingtransmitted a reference signal belongs, and therefore an error occurs ina channel estimation result. Non-Patent Document 3 and Non-PatentDocument 4 are directed to alleviating interference from an adjacentcell, and propose a grouping method for allocating sequences of highcross-correlation to the same cell as shown in FIG. 5 (Method 2). Byallocating these sequence numbers of high cross-correlation to the samecell as a group, it is possible to avoid the use of sequence numbers ofhigh cross-correlation between neighboring cells.

-   Non-Patent Document 1: Motorola, R1-062610, “Uplink Reference Signal    Multiplexing Structures for E-UTRA”, 3GPP TSG RAN WG1Meeting #46bis,    Soul, Korea, Oct. 9-13, 2006-   Non-Patent Document 2: Panasonic, R1-063183, “Narrow band uplink    reference signal sequences and allocation for E-UTRA”, 3GPP TSG RAN    WG1 Meeting #47, Riga, Latcia, Nov. 6-10, 2006-   Non-Patent Document 3: Huawei, R1-063356, “Sequence Assignment for    Uplink Reference Signal”, 3GPP TSG RAN WG1Meeting #47, Riga. Latvia,    Nov. 6-10, 2006-   Non-Patent Document 4: LGE, R1-070911, “Binding method for UL RS    sequence with different lengths”, 3GPP TSG RAN WG1Meeting #48, St.    Louis, USA, Feb. 12-16, 2007

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

However, if the above method 1 and method 2 are adopted at the sametime, interference is caused between sequences which have differentbandwidths and which have high cross-correlation between cells betweenwhich synchronization is established, and therefore the accuracy ofchannel estimation may degrade. This reason will be described below.

Assume that different cyclic shift sequence numbers (m) of the samesequence number (u) are allocated to cells (e.g. cells that belong tothe same base station) between which frame synchronization isestablished (method 1), and sequences numbers of high cross-correlationare allocated to ZC sequences of bandwidths in the same cell (method 2).In this case, if ZC sequences that are allocated to cells have the samesequence length and are allocated to the same frequency band, sequencesare orthogonal to each other, and, consequently, the correlation valuepeak in interference waves (i.e. the timing at which the power valueexceeds a predetermined value in a delay profile) are found in thedetection window (i.e. detection window for interference waves)corresponding to the cyclic shift sequence number m set in advance.

However, the orthogonality is not established completely betweensequences which have different bandwidths (i.e. different sequencelengths) and which have high cross-correlation, and, consequently, thewidth of a correlation value peak in interference waves may be spread ora position in which the correlation value peak is found may be shifted.As a result, interference wave peaks are detected in detection windowsfor desired waves, and correlation peaks in desired waves andcorrelation peaks in interference waves cannot be separated.Consequently, the influence of interference to desired waves increasesbetween different cyclic shift sequences of those different sequences.

It is therefore an object of the present invention to provide a cyclicshift sequence generating method, radio communication terminal apparatusand radio communication base station apparatus whereby, even with cyclicshift sequences which have different bandwidths and which havehigh-cross correlation, it is possible to prevent interference wavesfrom occurring in detection windows for desired waves and improve theaccuracy of channel estimation in the base station.

Means for Solving the Problem

The cyclic shift sequence generating method of the present inventionincludes generating a cyclic shift sequence by making a cyclic shiftinterval Δ1 between cyclic shift sequences of a Zadoff-Chu sequenceallocated to a single cell, different from a cyclic shift interval Δ2between cyclic shift sequences allocated between different cells betweenwhich frame synchronization is established.

The radio communication terminal apparatus of the present inventionemploys a configuration having: a cyclic shift sum calculating sectionthat calculates a sum of cyclic shifts that is equivalent to a sum ofcyclic shift intervals between an allocated cyclic shift sequence and areference cyclic shift sequence, based on a cyclic shift interval Δ1between cyclic shift sequences of a Zadoff-Chu sequence allocated to asingle cell and a cyclic shift interval Δ2, which is different from thecyclic shift interval Δ1, between cyclic shift sequences allocatedbetween different cells between which frame synchronization isestablished; a reference signal generating section that generates, as areference signal, the allocated cyclic shift sequence from the referencecyclic shift sequence, using the sum of cyclic shifts calculated; and atransmitting section that transmits the reference signal generated.

The radio communication base station apparatus of the present inventionemploys a configuration having: a dividing section that calculates acorrelation value by dividing a reference signal included in a receivedsignal using a Zadoff-Chu sequence; a cyclic shift sum determiningsection that determines a sum of cyclic shifts that is equivalent to asum of cyclic shift intervals between an allocated cyclic shift sequenceand a reference cyclic shift sequence, based on a cyclic shift intervalΔ1 between cyclic shift sequences of a Zadoff-Chu sequence allocated toa single cell and a cyclic shift interval Δ2, which is different fromthe cyclic shift interval. Δ1, between cyclic shift sequences allocatedbetween different cells between which frame synchronization isestablished; and an extracting section that extracts a correlation valuein a period including a correlation value of a desired sequence, basedon the sum of cyclic shifts determined.

Advantageous Effect of the Invention

According to the present invention, even with cyclic shift sequenceswhich have different bandwidths and which have high-cross correlation,it is possible to prevent interference waves from occurring in detectionwindows for desired waves and improve the accuracy of channel estimationin a base station.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates ZC sequences that can be used as reference signals;

FIG. 2 illustrates a state where different cyclic shift sequences of thesame sequence number are allocated between cells between which framesynchronization is established;

FIG. 3 illustrates the detection ranges corresponding to cyclic shiftsequence numbers and illustrates a state where a signal of a subjectcell is separated from received signals;

FIG. 4 illustrates a state where common cyclic shift sequence numbersare allocated in each RB;

FIG. 5 illustrates the method of grouping sequences disclosed inNon-Patent Document 3 and Non-Patent Document 4;

FIG. 6 illustrates a state where an interference peak occurs in thedetection window for a cyclic shift sequence allocated to a subjectcell;

FIG. 7 is a block diagram showing the configuration of a terminalaccording to Embodiment 1 of the present invention;

FIG. 8 illustrates a relationship between cyclic shift interval Δ1,which is the interval between cyclic shift sequences allocated in acell, and cyclic shift interval Δ2, which is the interval between cyclicshift sequences allocated between cells;

FIG. 9 is a block diagram showing the configuration of a base stationaccording to Embodiment 1 of the present invention;

FIG. 10 illustrates a state where a correlation value is extracted in amask processing section shown in FIG. 9;

FIG. 11A is a block diagram showing another configuration inside areference signal generating section shown in FIG. 7 (example 1);

FIG. 11B is a block diagram showing another configuration inside areference signal generating section shown in FIG. 7 (example 2);

FIG. 12 is a block diagram showing another configuration of a basestation according to Embodiment 2 of the present invention;

FIG. 13A illustrates a state where Δ2−Δ1 is increased or decreasedaccording to an increase or decrease of interference between adjacentcells to desired waves (type 1);

FIG. 13B illustrates a state where Δ2−Δ1 is increased or decreasedaccording to an increase or decrease of interference between adjacentcells to desired waves (type 2);

FIG. 13C illustrates a state where Δ2−Δ1 is increased or decreasedaccording to an increase or decrease of interference between adjacentcells to desired waves (type 3); and

FIG. 13D illustrates a state where Δ2−Δ1 is increased or decreasedaccording to an increase or decrease of interference between adjacentcells to desired waves (type 4).

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be explained below in detailwith reference to the accompanying drawings. Here, in the embodiments,the same components having the same functions will be allocated the samereference numerals and overlapping explanation will be omitted.

Embodiment 1

The configuration of terminal 100 according to Embodiment 1 of thepresent invention will be explained using FIG. 7. Radio frequency (RF)receiving section 102 performs receiving processing such asdown-conversion and A/D conversion on a signal received via antenna 101,and outputs the signal subjected to receiving processing to demodulatingsection 103. Demodulating section 103 performs equalization processingand demodulation processing on the signal outputted from RF receivingsection 102, and outputs the signal subjected to these processing todecoding section 104. Decoding section 104 performs decoding processingon the signal outputted from demodulating section 103, and extracts adata signal and control information. Further, in the extracted controlinformation, the cyclic shift sequence numbers are outputted to cyclicshift sum calculating section 105, and the RB allocation information isoutputted to mapping section 109.

Cyclic shift sum calculating section 105 calculates the sum of cyclicshifts based on the cyclic shift sequence number outputted from decodingsection 104 and cyclic shift intervals allocated to cells between whichframe synchronization is established (i.e. between cells) and to asingle cell (i.e. in a cell), and outputs the sum of cyclic shiftscalculated to cyclic shift section 107 in reference signal generatingsection 106.

Here, the cyclic shift sequence numbers that are allocated in a cell orbetween cells are determined in advance. For example, as shown in FIG.8, assume that cyclic shift sequence numbers m=0 and 1 are allocated tocell #1, and cyclic shift sequence numbers m=2 and 3 are allocated tocell #2. Further, assume that the cyclic shift interval is Δ1 betweencyclic shift sequences allocated in a cell, and the cyclic shiftinterval is Δ2 (≠Δ1) between cyclic shift sequences allocated betweencells. In the example shown in FIG. 8, the cyclic shift interval Δ1 isthree samples between the cyclic shift sequences (m=0 and 1) allocatedto cell #1 and between the cyclic shift sequences (m=2 and 3) allocatedto cell #2, and the cyclic shift interval Δ2 is four samples between thecyclic shift sequences (m=1 and 2) allocated between cell #1 and cell#2. In this case, if a base station reports m=2 to terminal 100, cyclicshift sum calculating section 105 of terminal 100 calculates Δ1+Δ2=7samples as the sum of cyclic shifts, which is equivalent to the sum ofcyclic shift intervals from the reference cyclic shift sequence of m=0.

Also, although a case has been described above where the cyclic shiftsequence numbers allocated to cells are determined in advance, theessential requirement is to employ a method whereby the relationshipsbetween the cyclic shift sequence numbers allocated in a cell and thecyclic shift sequence numbers allocated between cells, are held betweena base station and a terminal. For example, a base station may report toa terminal the relationships between the cyclic shift sequence numbersallocated in a cell and the cyclic shift sequence numbers allocatedbetween cells.

Also, although an example case has been described above where the cyclicshift sequence number in is reported, the absolute value of cyclic shiftinterval from a ZC sequence that is not cyclically shifted, may bereported on a per terminal basis (i.e. a base station reports (Δ1+Δ2) toterminal 100). In this case, a cyclic shift sum calculating section isunnecessary, and the configuration is employed for inputting thereported absolute value of the cyclic shift interval (e.g. Δ1+Δ2) incyclic shift section 107.

Reference signal generating section 106 is provided with cyclic shiftsection 107, discrete Fourier transform (DFT) section 108, mappingsection 109 and inverse discrete Fourier transform (IDFT) section 110,and generates a reference signal from a ZC sequence based on the sum ofcyclic shifts outputted from cyclic shift sum calculating section 105,and outputs the generated reference signal to multiplexing section 114.The configuration inside reference signal generating section 106 will beexplained below.

Cyclic shift section 107 cyclically shifts a ZC sequence outputted froma ZC sequence generating section that generates ZC sequences, by the sumof cyclic shifts outputted from cyclic shift sum calculating section105, and outputs the ZC sequence cyclically shifted to DFT section 108.

Here, the ZC sequence generating section specifies the transmissionbandwidth of a ZC sequence using RB allocation information in thecontrol information extracted in decoding section 104, and specifies theZC sequence length corresponding to the specified transmissionbandwidth. Further, the ZC sequence generating section specifies asequence number using information indicating sequence numbers allocatedto a belonging cell, in the control information extracted in decodingsection 104. The ZC sequence generating section then generates a ZCsequence using these sequence length and sequence number, and outputsthe ZC sequence to cyclic shift section 107.

DFT section 108 performs DFT (Discrete Fourier Transform) processing onthe ZC sequence outputted from cyclic shift section 107 to transform thetime domain signal into a frequency domain signal, and outputs the ZCsequence transformed into a frequency domain sequence to mapping section109.

Mapping section 109 maps the ZC sequence outputted from DFT section 108on the band corresponding to the transmission hand of terminal 100,based on the RB allocation information outputted from decoding section104, and outputs the mapped ZC sequence to IDFT section 110. IDFT(Inverse Discrete Fourier Transform) section 110 performs IDFTprocessing on the ZC sequence outputted from mapping section 109 andoutputs the ZC sequence subjected to IDFT processing to multiplexingsection 114.

Encoding section 111 encodes transmission data and outputs the encodeddata to modulating section 112. Modulating section 112 modulates theencoded data outputted from encoding section 111 and outputs themodulated signal to RB allocating section 113. RB allocating section 113allocates the modulated signal outputted from modulating section 112 toan RB and outputs the modulated signal allocated to the RB tomultiplexing section 114.

Multiplexing section 114 time-multiplexes the transmission dataoutputted from RB allocating section 113 and the ZC sequence (referencesignal) outputted from IDFT section 110, and outputs the multiplexedsignal to RF transmitting section 115. Here, the multiplexing method inmultiplexing section 114 is not limited to time multiplexing, and it isequally possible to adopt frequency multiplexing, code multiplexing orIQ multiplexing in a complex space.

RE transmitting section 115 performs transmission processing such as D/Aconversion, up-conversion and amplification on the multiplexed signaloutputted from multiplexing section 114, and transmits by radio thesignal subjected to transmission processing from antenna 101.

Next, the configuration of base station 150 according to Embodiment 1 ofthe present invention will be explained using FIG. 9. Encoding section151 encodes transmission data and control signal, and outputs theencoded data to modulating section 152. Here, the control signalincludes a cyclic shift sequence number that is allocated to a cell.Modulating section 152 modulates the encoded data and outputs themodulated signal to RF transmitting section 153. RE transmitting section153 performs transmission processing such as D/A conversion,up-conversion and amplification on the modulated signal, and transmitsby radio the signal subjected to transmission processing from antenna154.

RF receiving section 155 performs receiving processing such asdown-conversion and A/D conversion on a signal received via antenna 154,and outputs the signal subjected to receiving processing todemultiplexing section 156. Demultiplexing section 156 demultiplexes thesignal outputted from RF receiving section 155 into the referencesignal, data signal and control signal, outputs the reference signal toDFT (Discrete Fourier Transform) section 157 and outputs the data signaland the control signal to DFT section 165.

DFT section 157 performs DFT processing on the reference signaloutputted from demultiplexing section 156 to transform a time domainsignal into a frequency domain signal, and outputs the reference signaltransformed into a frequency domain signal to demapping section 159 ofchannel estimating section 158.

Channel estimating section 158 is provided with demapping section 159,dividing section 160, IDFT (Inverse Discrete Fourier Transform) section161, mask processing section 162 and DFT section 163, and estimates achannel based on the reference signal outputted from DFT section 157.The configuration inside channel estimating section 158 will beexplained below in detail.

Demapping section 159 extracts parts corresponding to the transmissionbands of terminals, from the signal outputted from DFT section 157, andoutputs the extracted signals to dividing section 160. Dividing section160 divides the signal outputted from demapping section 159 by the abovereference ZC sequence (i.e. the ZC sequence of cyclic shift sequencenumber m=0), and outputs the division result (i.e. correlation value) toIDFT section 161. IDFT section 161 performs IDFT processing on thesignal outputted from dividing section 160, and outputs the signalsubjected to IDFT processing to mask processing section 162.

By performing mask processing on the signal outputted from IDFT section161 based on a sum of cyclic shifts outputted from cyclic shift sumdetermining section 164, which will be described later, mask processingsection 162 as an extracting section extracts the correlation value inthe period (i.e. detection window) in which there is the correlationvalue of the desired cyclic shift sequence, and outputs the extractedvalue to DFT section 163.

DFT section 163 performs DFT processing on the correlation valueoutputted from mask processing section 162, and outputs the correlationvalue subjected to DFT processing to frequency domain equalizationsection 167. Here, the signal outputted from DFT section 163 representsthe frequency variation in the channel.

In cyclic shift sum determining section 164, the same content as set incyclic shift sum calculating section 105 of terminal 100 is set inadvance. That is, as in the example shown in FIG. 8, the cyclic shiftsequence numbers m=0 and 1 are allocated to cell #1, and the cyclicshift sequence numbers m=2 and 3 are allocated to cell #2. Also, thecyclic shift interval Δ1 is three samples between the cyclic shiftsequences (m=0 and 1) allocated to cell #1 and between the cyclic shiftsequences (m=2 and 3) allocated to cell #2, and the cyclic shiftinterval Δ2 is four samples between the cyclic shift sequences (m=1 and2) allocated between cell #1 and cell #2.

Here, if base station 150 reports to terminal 100 that terminal 100transmits the ZC sequence of m=2, base station 150 knows that the ZCsequence of the sum of cyclic shifts of 7 samples is transmitted fromterminal 100, and, consequently, mask processing section 162 performsextraction only in the period (detection window) corresponding to theabove ZC sequence. Also, the detection window width may be commonbetween a plurality of cyclic shift intervals. That is, the detectionwindow width needs not be changed based on the cyclic shift intervalbetween cells or in a cell. Here, the detection window width may bechanged based on the cyclic shift interval between cells or in a cell.

DFT section 165 performs DFT processing on the data signal and controlsignal outputted from demultiplexing section 156 to transform the timedomain signals into frequency domain signals, and outputs the datasignal and control signal transformed into a frequency domain signal todemapping section 166.

Demapping section 166 extracts parts of the data signal and controlsignal corresponding to the transmission bands of terminals, and outputsthe extracted signals to frequency domain equalization section 167.

Frequency domain equalization section 167 performs equalizationprocessing on the data signal and control signal outputted fromdemapping section 166, using the signal (i.e. the frequency response ofthe channel) outputted from DFT section 163 in channel estimatingsection 158, and outputs the signals subjected to equalizationprocessing to IDFT section 168.

IDFT section 168 performs IDFT processing on the data signal and controlsignal outputted from frequency domain equalization section 167, andoutputs the signals subjected to IDFT processing to demodulating section169. Demodulating section 169 performs demodulation processing on thesignals subjected to IDFT processing, and outputs the signals subjectedto demodulation processing to decoding section 170. Decoding section 170performs decoding processing on the signals subjected to demodulationprocessing, and extracts received data.

Next, the above extraction of a correlation value in mask processingsection 162 of base station 150 will be explained using FIG. 10. In FIG.10, the correlation values represented by the solid lines show thecorrelation values of desired waves, and the correlation valuesrepresented by the dotted lines show the correlation values ofinterference waves. Also, the detection window represented by the solidlines show the detection window for the desired waves. Here, the signalof cell #1 is the desired wave. As shown in this figure, it isacknowledged that the correlation values of interference waves are foundoutside the range of the detection window (i.e. outside the detectionwindow) for the desired waves. This is because a position in whichcorrelation of interference waves is caused, changes based on changes ofa cyclic shift interval. By this means, it is possible to alleviateinterference between adjacent cells and improve the accuracy of channelestimation.

As described above, according to Embodiment 1, by determining in advancecyclic shift sequence numbers allocated to cells and holding therelationship of Δ1<Δ2 where Δ1 is the cyclic shift interval betweencyclic shift sequences allocated in a cell and Δ2 is the cyclic shiftinterval between cyclic shift sequences allocated between cells, it ispossible to find correlation values of interference waves outside therange of the detection window for the desired waves and alleviateinterference between adjacent cells, thereby improving the accuracy ofchannel estimation.

Also, the processing method in base station 150 is not limited to theabove, and the essential requirement is that the method can separate thedesired waves from interference waves. For example, based on the sum ofcyclic shifts outputted from cyclic shift sum determining section 164, aZC sequence acquired by cyclically shifting the reference ZC sequence ofm=0 is outputted to dividing section 160. Dividing section 160 divides asignal outputted from demapping section 159 by a ZC sequence, which isacquired by cyclically shifting a ZC sequence through the sum of cyclicshifts received as input (i.e. the same sequence as a cyclic shift ZCsequence transmitted on the transmitting side), and outputs the divisionresult (i.e. correlation value) to IDFT section 161. By performing maskprocessing on signals outputted from IDFT section 161, mask processingsection 162 extracts the correlation value in the period in which thereis the correlation value of the desired cyclic shift sequence (i.e. thefirst detection window if division processing is performed using a ZCsequence acquired by performing a cyclic shift by the sum of cyclicshifts), and outputs the extracted correlation value to DFT section 163.By these processing, it is possible to separate the desired waves andthe interference waves from received waves.

Also, although a case has been described with the present embodimentwhere reference signal generating section 106 in terminal 100 is asshown in FIG. 7, it is equally possible to employ the configurationsshown in FIG. 11A and FIG. 11B. In reference signal generating section106 shown in FIG. 11A, a cyclic shift section is provided after an IDFTsection. This cyclic shift section needs to perform a cyclic shift usingthe sum of cyclic shifts talking into account oversampling.

Also, in reference signal generating section 106 shown in FIG. 11B, aphase rotating section is provided after a DFT section. Instead ofperforming a cyclic shift in the time domain, this phase rotatingsection performs processing, which is equivalent to a cyclic shift inthe time domain, in the frequency domain. That is, the amount of phaserotation corresponding to the sum of cyclic shifts is allocated to eachsubcarrier. Here, it is known from the relationship of the Fouriertransform pair in equation 5 that a cyclic shift in the time domain isequivalent to a phase rotation in the frequency domain.

[5]

X(n)exp(−j2πnΔ/N)=DFT[x(k−Δ)],DFT[ ]:Discrete Fourier Transform

x(k−Δ)=IDFT{X(n)exp(−j2πnΔ/N)}IDFT[ ]:Inverse Discrete FourierTransform  (Equation 5)

Although reference signal generating section 106 shown in FIG. 11A andFIG. 11B generate a ZC sequence in the time domain (equation 2),reference signal generating section 106 may generate a ZC sequence inthe frequency domain, provided that a Fourier transform pair of a ZCsequence is mapped by ZC sequences of the same sequence length. That is,instead of generating a ZC sequence and performing DFT processing, it ispossible to directly generate a ZC sequence in the frequency domainwithout using a DFT section (equation 4).

Also, although a case has been described with the present embodimentwhere the cyclic shift interval Δ2 between cells is greater than thecyclic shift interval Δ1 in a cell (Δ1<Δ2), the present invention is notlimited to this, and it is equally possible to make Δ2 smaller than Δ1(Δ1>Δ2) if, for example, it is known in advance that sequences of highcross-correlation are not used between different cells. Also, it ispossible to combine Δ1<Δ2 and Δ1>Δ2, or use only one of Δ1<Δ2 and Δ1>Δ2.Further, it is equally possible to use a combination of the cases ofΔ1<Δ2 and Δ1=Δ2, or a combination of Δ1>Δ2 and Δ1=Δ2. For example, theremay be a base station that performs an allocation with Δ1<Δ2 and a basestation that performs an allocation with Δ1=Δ2.

Embodiment 2

A case will be explained with Embodiment 2 of the present inventionwhere, based on interference from an adjacent cell, the cyclic shiftinterval Δ1 between cyclic shift sequences of a Zadoff-Chu sequenceallocated in the same cell, and the cyclic shift interval Δ2 betweencyclic shift sequences allocated between different cells between whichframe synchronization is established, are controlled. Here, assume thatone from a plurality of sequence groups is allocated to each basestation, and each sequence group has the sequence numbers of ZCsequences allocated as the ZC sequences of transmission bandwidths.

The configuration of the terminal according to Embodiment 2 of thepresent invention will be explained. Here, cyclic shift sum calculatingsection 105 will be explained using FIG. 7 because the configuration ofa terminal according to the present embodiment is similar to theconfiguration shown in FIG. 7 of Embodiment 1, and differs from theconfiguration shown in FIG. 7 only in receiving control informationincluding cyclic shift sequence numbers and sequence group numbers froma base station, in the terminal, and in part of the functions of cyclicshift sum calculating section 105.

Cyclic shift sum calculating section 105 calculates the sum of cyclicshifts using a cyclic shift sequence number and sequence group numberoutputted from decoding section 104. To be more specific, cyclic shiftsum calculating section 105 estimates a sequence group allocated to thesubject base station based on the sequence group number, and decideswhether the estimated sequence group is formed with a combination ofsequences of high cross-correlation or the estimated sequence group isformed with a combination of sequences of low cross-correlation. Next,cyclic shift sum calculating section 105 determines the sum of cyclicshifts using the cyclic shift sequence number outputted from decodingsection 104 and the relationship between the cyclic shift interval Δ1and the cyclic shift interval Δ2 derived from the above decision result(which will be described later), where the cyclic shift interval Δ1 isthe interval between sequences in a cell and the cyclic shift intervalΔ2 is the interval between sequences between cells.

As a method of deciding whether cross-correlation is high orcross-correlation is low, when two ZC sequences have the sequencenumbers (u1, u2) and the sequence lengths (N1, N2), thecross-correlation is decided high if the difference between the ratios(u1/N1) and (u2/N2) is equal to or less than a predetermined threshold,and the cross-correlation is decided low if the difference between theratios is greater than a predetermined threshold.

Next, the relationship between the cyclic shift interval Δ1 and thecyclic shift interval Δ2 based on the decision result of thecross-correlation, will be explained, where the cyclic shift interval Δ1is the interval between sequences in a cell and the cyclic shiftinterval Δ2 is the interval between sequences between cells. In thesequence group of high cross-correlation, as shown in FIG. 8, the cyclicshift interval Δ1 between cyclic shift sequences allocated in a cell andthe cyclic shift interval Δ2 between cyclic shift sequences allocatedbetween cells, hold in advance the relationship that the cyclic shiftinterval between cells is greater than the cyclic shift interval in acell (Δ1<Δ2). Also, the sequence group of low cross-correlation holdsthe relationship that the cyclic shift interval in a cell is equal to orgreater than the cyclic shift interval between cells (Δ1≧Δ2).

In this case, the sequence group of high cross-correlation providessignificant interference between adjacent cells, and, by making thissequence group hold the relationship that the cyclic shift intervalbetween cells is greater than the cyclic shift interval in a cell(Δ1<Δ2), it is possible to reduce interference between adjacent cells.By contrast, the sequence group of low cross-correlation providesinsignificant interference between adjacent cells, and, by making thissequence group hold the relationship that the cyclic shift intervalbetween cells is smaller than the cyclic shift interval in a cell(Δ1≧Δ2), it is possible to shorten the cyclic shift interval in eachcyclic shift sequence and therefore increase the number of cyclic shiftsequences.

Also, sequence group information may be information that allows indirectestimation of sequence groups. For example, one sequence group isallocated to each cell, and, consequently, it may be possible toestimate sequence group information from a cell ID.

Next, the configuration of a base station according to Embodiment 2 ofthe present invention will be explained. Here, cyclic shift sumdetermining section 164 will be explained using FIG. 9 because theconfiguration of a base station according to the present embodiment issimilar to the configuration shown in FIG. 9 of Embodiment 1, anddiffers from the configuration shown in FIG. 9 only in part of thefunctions of cyclic shift sum determining section 164.

In cyclic shift sum determining section 164, the same content as set incyclic shift sum calculating section 105 of a terminal is set inadvance. That is, a sequence group of high cross-correlation holds therelationship of Δ1<Δ2, and a sequence group of low cross-correlationholds the relationship of Δ1≧Δ2. For example, the cyclic shift sequencenumbers m=0 and 1 are set to be allocated to cell #1, and the cyclicshift sequence numbers m=2 and 3 are set to be allocated to cell #2.Further, a sequence group of high cross-correlation holds therelationship of Δ1=3 and Δ2=4, and a sequence group of lowcross-correlation holds the relationship of Δ1=3 and Δ2=3.

In this case, if a base station reports terminal 100 that terminal 100transmits the ZC sequence of m=2, the base station to which a sequencegroup of high cross-correlation is allocated, knows that the ZC sequenceof the sum of cyclic shifts of 7 samples is transmitted from terminal100, while the base station to which a sequence group of lowcross-correlation is allocated, knows that the ZC sequence of the sum ofcyclic shifts of 6 samples is transmitted from terminal 100. Maskprocessing section 162 performs extraction only in the period (detectionwindow) corresponding to the samples of the sum of cyclic shifts.

Thus, according to Embodiment 2, a sequence group of highcross-correlation provides significant interference between cells, and,by making this sequence group hold the relationship of Δ1<Δ2, it ispossible to reduce interference between adjacent cells. Also, a sequencegroup of low cross-correlation provides insignificant interferencebetween cells, and, by making this sequence group hold the relationshipof Δ1≧Δ2, it is possible to shorten the cyclic shift interval in eachcyclic shift sequence and therefore increase the number of cyclic shiftsequences.

Also, although a case has been described above with Embodiment 2 wheresequence groups are allocated to a base station, the present inventionis not limited to this, and is also applicable to cases where a sequencegroup of low cross-correlation is allocated to a ZC sequence of a longsequence length and a sequence group of high cross-correlation isallocated to a ZC sequence of a short sequence length. For example, agroup of low cross-correlation is allocated to a ZC sequence of a longsequence length (e.g. a ZC sequence having a transmission bandwidthequal to or greater than 10 RB's), and a group of high cross-correlationis allocated to a ZC sequence of a short sequence length (e.g. a ZCsequence having a transmission bandwidth less than 10 RB's). In thiscase, the sequence group of high cross-correlation holds therelationship that the cyclic shift interval between cells is greaterthan the cyclic shift interval in a cell (Δ1<Δ2), and the sequence groupof low cross-correlation holds the relationship that the cyclic shiftinterval between cells is equal to or less than the cyclic shiftinterval in a cell Δ1≧Δ2. Also, although the above decision is madebased on the cross-correlation in sequence groups, if thecross-correlation between adjacent cells can be decided instead of thecross-correlation in sequence groups, other methods are possible.

Also, a case has been described above with the present embodiment wherethe cyclic shift intervals Δ1 and Δ2 are controlled based on thecross-correlation in sequence groups allocated to cells between whichsynchronization is established. However, the present invention is notlimited to this, and, for example, a base station may measureinterference power from adjacent cells to the desired waves (i.e. ZCsequence) and control the cyclic shift intervals Δ1 and Δ2. Theconfigurations of a terminal and base station in this case will beexplained below.

Cyclic shift sum calculating section 105 will be explained using FIG. 7because the configuration of another terminal according to Embodiment 2of the present invention is similar to the configuration shown in FIG. 7of Embodiment 1, and differs from the configuration shown in FIG. 7 onlyin receiving control information including cyclic shift sequence numbersand interference power information showing interference power betweenadjacent cells from a base station, in the terminal, and in part of thefunctions of cyclic shift sum calculating section 105.

Cyclic shift sum calculating section 105 calculates the sum of cyclicshifts using a cyclic shift sequence number and interference powerinformation outputted from decoding section 104. Here, in cyclic shiftsum calculating section 105, high interference power holds therelationship that the cyclic shift interval between cells is greaterthan the cyclic shift interval in a cell (Δ1<Δ2), and low interferencepower holds the relationship that the cyclic shift interval betweencells is equal to or less than the cyclic shift interval in a cell(Δ1≧Δ2). Further, cyclic shift sum calculating section 105 calculatesthe sum of cyclic shifts from a cyclic shift sequence number and thevalues of Δ1 and Δ2 that are decided based on the magnitude ofinterference power.

Next, the configuration of another base station according to Embodiment2 of the present invention will be explained using FIG. 12. Here, basestation 200 of FIG. 12 differs from FIG. 9 in adding interference powermeasuring section 201.

Interference power measuring section 201 measures interference powerusing signals outputted from IDFT section 161. For example, interferencepower measuring section 201 measures interference power by measuring thepower of signals outside the period (i.e. detection window)corresponding to the ZC sequence for the subject mobile station, amongsignals outputted from IDFT section 161. The measured interference poweris outputted to cyclic shift sum determining section 164 and encodingsection 151 via a signal line (not shown). Also, in cyclic shift sumdetermining section 164, the same content as set in cyclic shift sumcalculating section 105 of a terminal is set in advance. That is, highinterference power holds the relationship that the cyclic shift intervalbetween cells is greater than the cyclic shift interval in a cell(Δ1<Δ2), and low interference power holds the relationship that thecyclic shift interval between cells is equal to or less than the cyclicshift interval in a cell (Δ1≧Δ2). Further, cyclic shift sum calculatingsection 164 calculates the sum of cyclic shifts from a cyclic shiftsequence number and the values of Δ1 and Δ2 that are decided based onthe magnitude of interference power.

Embodiment 3

A case will be explained with Embodiment 3 of the present inventionwhere Δ2−Δ1 is increased or decreased according to an increase ordecrease of adjacent-cell interference to desired waves. Here, thefunction f of Δ2−Δ1=f (1/inter-cell interference) is defined, and Δ1 andΔ2 are changed based on this relationship. For example, if Δ1 is fixedand Δ2 is variable, the following four types are defined.

First, FIG. 13A illustrates the first type. As shown in this figure,when interference power is smaller, the cyclic shift interval Δ2 becomessmaller. Also, when interference power is larger, the cyclic shiftinterval Δ2 becomes larger.

Next, FIG. 13B illustrates the second type. As shown in this figure,when interference power is smaller, the cyclic shift interval Δ2 becomessmaller. Also, when interference power is larger, the cyclic shiftinterval Δ2 becomes larger. Here, a threshold is provided for1/interference power, and the cyclic shift interval Δ2 is fixed at themaximum value when 1/interference power is equal to or less than thethreshold.

Next, FIG. 13C illustrates the third type. As shown in this figure, wheninterference power is larger, the cyclic shift interval Δ2 becomeslarger. Also, when interference power is smaller, the cyclic shiftinterval Δ2 becomes smaller. Here, a threshold is provided for1/interference power, and the cyclic shift interval Δ2 is fixed at theminimum value when 1/interference power is greater than the threshold.

FIG. 13D illustrates the fourth type. As shown in this figure, wheninterference power is larger, the cyclic shift interval Δ2 becomeslarger. Also, when interference power is smaller, the cyclic shiftinterval Δ2 becomes smaller. Here, threshold 1 and threshold 2(>threshold 1) are provided for 1/interference power, and the cyclicshift interval Δ2 is fixed at the maximum value when 1/interferencepower is equal to or less than threshold 1, and the cyclic shiftinterval Δ2 is fixed at the minimum value when 1/interference power isgreater than threshold 2.

Here, although Δ1 is fixed and Δ2 is variable, it is equally possible tomake Δ2 fixed and Δ1 variable. Also, both Δ1 and Δ2 can be fixed or madevariable.

As described above, according to Embodiment 3, it is possible toalleviate interference between cells by increasing or decreasing thecyclic shift interval Δ2 and cyclic shift interval Δ1 based on anincrease or decrease of interference between cells, where the cyclicshift interval Δ2 is the interval between cyclic shift sequencesallocated between cells and where the cyclic shift interval Δ1 is theinterval between cyclic shift sequences allocated in a cell.

Although example cases have been described above with embodiments usingZC sequences having an odd-numbered sequence length, the presentinvention is also applicable to ZC sequences having an even-numberedsequence length. Also, the present invention is applicable to GCL(Generalized. Chirp Like) sequences including ZC sequences. Also, thepresent invention is also applicable to binary sequences and other CAZACsequences using cyclic shift sequences or ZCZ sequences for codesequences. For example, there are Frank sequences, other CAZAC sequences(including sequences generated by a computer), and PN sequences such asM sequences and gold sequences.

Also, although example cases have been described above with embodimentsusing Zadoff-Chu sequences, the present invention is also applicable tomodified Zadoff-Chu sequences acquired by cyclically extending ortruncating Zadoff-Chu sequences. Generally, a ZC sequence having asequence length N of a prime number cannot be adjusted to the number ofsubcarriers in the transmission band. Therefore, in order to adjust a ZCsequence having a sequence length N of a prime number to the number ofsubcarriers in the transmission band, studies are underway for themethod of generating reference signals having the number of subcarriersin the transmission band by cyclically extending ZC sequences having alength of a prime number, and for the method of generating Zadoff-Chusequences based on the number of subcarriers in the transmission band bycutting, that is, truncating ZC sequences having a length of a primenumber. The present invention may be applicable to those modified ZCsequences subjected to cyclic expansion or truncation.

Also, although an example case has been described above where CAZACsequences and their cyclic shift sequences are utilized as uplinkreference signals, the present invention is not limited to this. Thepresent invention is also applicable to cases where reference signalsfor uplink channel quality estimation, preamble sequences for randomaccess and reference signals for downlink synchronization channels aretransmitted in different transmission bands between cells using cyclicshifts.

Further, the present invention is also applicable to cases where a CAZACsequence is used as a spreading code in code division multiplexing(“CDM”) or in code division multiple access (“CDMA”).

Also, although example cases have been described above with embodimentswhere a mobile station transmits data and reference signal to a basestation, the present invention is applicable to cases of transmissionfrom the base station to the mobile station.

Also, although the above embodiments have explained problems that arecaused in ZC sequences of different bandwidths, the similar problems arecaused in transmission bands of the same bandwidth (in which part of thetransmission bands overlap). These problems can be solved by the aboveembodiments.

Although a case has been described above with the above embodiments asan example where the present invention is implemented with hardware, thepresent invention can be implemented with software.

Furthermore, each function block employed in the description of each ofthe aforementioned embodiments may typically be implemented as an LSIconstituted by an integrated circuit. These may be individual chips orpartially or totally contained on a single chip. “LSI” is adopted herebut this may also be referred to as “IC,” “system LSI,” “super LSI,” or“ultra LSI” depending on differing extents of integration.

Further, the method of circuit integration is not limited to LSI's, andimplementation using dedicated circuitry or general purpose processorsis also possible. After LSI manufacture, utilization of an FPGA (FieldProgrammable Gate Array) or a reconfigurable processor where connectionsand settings of circuit cells in an LSI can be reconfigured is alsopossible.

Further, if integrated circuit technology comes out to replace LSI's asa result of the advancement of semiconductor technology or a derivativeother technology, it is naturally also possible to carry out functionblock integration using this technology. Application of biotechnology isalso possible.

The disclosure of Japanese Patent Application No. 2007-160347, filed on.Jun. 18, 2007, including the specification, drawings and abstract, isincorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

Even with cyclic shift sequences which have different bandwidths andwhich have high cross-correlation, the cyclic shift sequence generatingmethod, radio communication terminal apparatus and radio communicationbase station apparatus according to the present invention can preventinterference waves from occurring in the detection windows forinterference waves and improve the accuracy of channel estimation in thebase station, and the method and apparatuses are applicable to, forexample, mobile communication systems.

1. A terminal apparatus comprising: a reception section configured toreceive control information transmitted from a base station; agenerating section configured to generate a reference signal based on acyclic shift number out of a plurality of cyclic shift numbers, thecyclic shift number being given by the control information; and atransmission section configured to transmit the reference signal,wherein the plurality of cyclic shift numbers includes two cyclic shiftnumbers, which are next to each other in order of cyclic shift numberand a difference between which is a first interval, and two cyclic shiftnumbers, which are next to each other in order of cyclic shift numberand a difference between which is a second interval different from thefirst interval.
 2. The terminal apparatus according to claim 1, whereinthe first interval is smaller than the second interval.
 3. The terminalapparatus according to claim 1, wherein a difference between the x-thlargest cyclic shift number and the (x−1)-th largest cyclic shift numberout of the plurality of cyclic shift numbers is the first interval orthe second interval.
 4. The terminal apparatus according to claim 3,wherein whether the difference between the x-th largest cyclic shiftnumber and the (x−1)-th largest cyclic shift number is the firstinterval or the second interval is shared between the terminal apparatusand the base station.
 5. The terminal apparatus according to claim 1,wherein the reference signal is generated based on a Zadoff-Chu sequenceand the cyclic shift number.
 6. The terminal apparatus according toclaim 1, wherein a difference between the x-th largest cyclic shiftnumber and the (x−1)-th largest cyclic shift number out of the pluralityof cyclic shift numbers is the second interval, and a difference betweenthe (x+1)-th largest cyclic shift number and the x-th largest cyclicshift number out of the plurality of cyclic shift numbers is the firstinterval.
 7. The terminal apparatus according to claim 1, wherein adifference between the x-th largest cyclic shift number and the (x−1)-thlargest cyclic shift number out of the plurality of cyclic shift numbersis the first interval, and a difference between the (x+1)-th largestcyclic shift number and the x-th largest cyclic shift number out of theplurality of cyclic shift numbers is the second interval.
 8. Theterminal apparatus according to claim 1, wherein a minimum cyclic shiftnumber out of the plurality of cyclic shift numbers is zero.
 9. A basestation apparatus comprising: a transmission section configured totransmit control information to a terminal; a reception sectionconfigured to receive a reference signal, which is generated based on acyclic shift number out of a plurality of cyclic shift numbers and whichis transmitted from the terminal, the cyclic shift number being given bythe control information; and wherein the plurality of cyclic shiftnumbers includes two cyclic shift numbers, which are next to each otherin order of cyclic shift number and a difference between which is afirst interval, and two cyclic shift numbers, which are next to eachother in order of cyclic shift number and a difference between which isa second interval different from the first interval.
 10. The basestation apparatus according to claim 9, wherein the first interval issmaller than the second interval.
 11. The base station apparatusaccording to claim 9, wherein a difference between the x-th largestcyclic shift number and the (x−1)-th largest cyclic shift number out ofthe plurality of cyclic shift numbers is the first interval or thesecond interval.
 12. The base station apparatus according to claim 11,wherein whether the difference between the x-th largest cyclic shiftnumber and the (x−1)-th largest cyclic shift number is the firstinterval or the second interval is shared between the terminal and thebase station apparatus.
 13. The base station apparatus according toclaim 9, wherein the reference signal is generated based on a Zadoff-Chusequence and the cyclic shift number.
 14. The base station apparatusaccording to claim 9, wherein a difference between the x-th largestcyclic shift number and the (x−1)-th largest cyclic shift number out ofthe plurality of cyclic shift numbers is the second interval, and adifference between the (x+1)-th largest cyclic shift number and the x-thlargest cyclic shift number out of the plurality of cyclic shift numbersis the first interval.
 15. The base station apparatus according to claim9, wherein a difference between the x-th largest cyclic shift number andthe (x−1)-th largest cyclic shift number out of the plurality of cyclicshift numbers is the first interval, and a difference between the(x+1)-th largest cyclic shift number and the x-th largest cyclic shiftnumber out of the plurality of cyclic shift numbers is the secondinterval.
 16. The base station apparatus according to claim 9, wherein aminimum cyclic shift number out of the plurality of cyclic shift numbersis zero.
 17. A communication method comprising: receiving controlinformation transmitted from a base station; generating a referencesignal based on a cyclic shift number out of a plurality of cyclic shiftnumbers, the cyclic shift number being given by the control information;and transmitting the reference signal, wherein the plurality of cyclicshift numbers includes two cyclic shift numbers, which are next to eachother in order of cyclic shift number and a difference between which isa first interval, and two cyclic shift numbers, which are next to eachother in order of cyclic shift number and a difference between which isa second interval different from the first interval.
 18. A communicationmethod comprising: transmitting control information to a terminal;receiving a reference signal, which is generated based on a cyclic shiftnumber out of a plurality of cyclic shift numbers and which istransmitted from the terminal, the cyclic shift number being given bythe control information; and wherein the plurality of cyclic shiftnumbers includes two cyclic shift numbers, which are next to each otherin order of cyclic shift number and a difference between which is afirst interval, and two cyclic shift numbers, which are next to eachother in order of cyclic shift number and a difference between which isa second interval different from the first interval.